In a water environment the minerals necessary to life are held in
solution or lie in bottom sediments. They become available to animal
life after being absorbed by plants, both large floating or rooted
plants and tiny floating ones called phytoplankton; because the
phytoplankton are found everywhere in the sea, they play a larger role.
The phytoplankton concentrate minerals and become food for
filter-feeding fish and other creatures, including the smaller
zooplankton,[14] which, in turn, are food for other organisms. Thus the
minerals enter extremely complex food chains. The cycles of nutrition
are completed when fish and plants die and decomposition again makes the
minerals available to the phytoplankton.